The Internal floating piston (IFP) is commonly used to maintain separation of the oil from the gas during the operation of the shock absorber. The separation prevents the oil from mixing with the gas thereby significantly improving the dampening characteristics of the shock. Accordingly, the internal floating piston is a highly desirable component in a shock. In order for the internal floating piston to be effective, the internal floating piston must act as a permanent barrier and the oil and gas must be located on opposite sides of the internal floating piston. This requires physically locating the oil and gas on opposite sides of the internal floating piston while charging the shock with oil and gas. The charging process can be realized either during or after the construction of the shock. Charging of the shock during construction complicates the construction and increases the manufacturing costs. Charging of the shock after construction necessitates two valves (e.g., two Schrader valves); one for oil and another for gas. This also complicates the construction and increases the manufacturing costs and requires an additional step to charge the shock with oil and gas.
In the case of air shocks, the increased work and costs prohibit internal floating pistons from being used. To date, all commercially available air shocks operate with emulsion based dampening characteristics because no shock absorber manufacturer installs internal floating pistons in air shocks (see Fred Williams, Air Shock Technical-Air Shocks 4 Rocks, non-patent references).
Since the gas permeable internal floating piston is able to separate the oil from the gas and maintain that separation during the operation of the shock, then utilization of the gas permeable internal floating piston in place of an ordinary internal floating piston promises simpler construction, reduced manufacturing costs, and easier set-up methods for the shock. These benefits and other related benefits are disclosed herein.
Disclosed in patent application Ser. No. 13/854,055 is the multiple stage air shock; and, disclosed in patent application Ser. No. 14/935,423 is a process for constructing the multiple stage air shock whereby the process introduces several features including the determination of various lengths and spring rates that are absent in the art. The multiple stage air shock possesses both dampening and suspension spring capabilities whereby the dampening capability is based on an emulsion comprised of a mixture of oil and gas.
The emulsion is well known in the art and is considered to provide unpredictable dampening properties in a shock absorber, which in turn, lead to unpredictable handling characteristics for the vehicle. The deficiency of the emulsion lies in the mixing of the oil with the gas. The mixing permits the gas to alter the movement of the oil through the working piston whereby the movement of the oil through the working piston defines the dampening properties. One of the techniques used to improve the dampening properties of an emulsion based shock absorber is to prevent the oil from mixing with the gas, in effect eliminate the emulsion, which is achieved by simply separating the oil from the gas.
A common method of separating the oil from the gas is by installing an internal floating piston into the working tube of the shock absorber. The oil and gas are placed on opposing sides of the internal floating piston thereby effectively separating the oil from the gas. Such a method represents the basis for a shock absorber known as the monotube shock absorber whereby the monotube shock absorber is revered for its dampening properties. In a monotube shock absorber, the oil can be separated from the gas by attaching check valves to each end of the working tube whereby the check valve serves to add the oil and gas to the working tube. Then the oil is added via one check valve while the gas is added via the other check valve. This addition process serves to place the oil and gas on opposing sides of the internal floating piston.
Such an addition process is not realistic for the multiple stage air shock. The multiple stage air shock involves interconnecting components that serve in a manner like a working tube. However, one of the ends of one interconnecting component travels into another interconnecting component during the operation of the air shock, and therefore, is not available for receiving a check valve. A more realistic method would involve the addition of the oil and gas into the interconnecting component via a single check valve and then separating the oil from the gas in an autonomous fashion. In this case, the autonomous fashion refers to the selection of materials used in the construction of the internal floating piston. In principle, an internal floating piston that allows the gas but not the oil to pass through its structure would represent a viable means to separate the oil from the gas. This means serves as the basis for the present invention.